There is increasing demand for higher data rates in wireless networks to support sophisticated services such as cloud computing. Wireless systems are adopting more aggressive resource reuse, which leads to increased co-channel interference. In heterogeneous networks (HetNet), the co-channel interference may be especially problematic, because the network deployment may follow an ad hoc style. This may lead to increasing inter-cell interference (ICI) for cell-edge users.
One interference management technique is coordinated multi-point (CoMP) proposed in the third Generation Partnership Project (3GPP) Long-Term Evolution-Advanced (LTE-Advanced). CoMP is also known as network multiple input multiple output (MIMO) or base station (BS) cooperation. CoMP exploits ICI by facilitating channel state information (CSI) and/or user data to be shared and jointly processed by multiple base stations.
In CoMP, clustering determines the pattern of cooperating base stations. Two types of clustering approaches are static clustering and dynamic clustering. In both clustering approaches, the CSI is either shared among network entities or collected by a central controller.
The CSI may be imperfect due to imperfect in channel estimation and the delay in transmitting the CSI. In CoMP, the CSI is propagated over backhaul networks, which are constrained in capacity, leading to lost and delayed CSI. For example, in LTE-Advanced, the standard interface for inter-BS communications, X2, is designed to allow a latency of 20 ms for control plan messages, with an expected typical latency of 10 ms.